In higher speed line printing, it has been found that the band or belt type printer has certain advantages over the drum type printer. The band is caused to be driven in continuous manner along a line of printing wherein a plurality of hammers are aligned to be selectively driven into impact with paper or like record media and an associated ribbon and against type characters on the print band. Since it is desired to control the speed of the print band within close tolerances so as to permit driving of the hammers into proper registration with the characters on the print band, the band speed is an important aspect of the printer. The prior art has utilized timing marks on the band, and timing pulses derived from such marks on the print band have served to control the speed of the band by means of servo motor control.
Additionally, it is well known that a type character band includes a plurality of font sets wherein each character of every font set is continuously scanned by the control apparatus so as to fire the selected hammers at the precise time that the characters pass the various print positions. The band may include marks thereon which correspond to the characters and may also include marks to indicate the various font sets with sensing or detecting means being provided to send pulses to the control mechanism at precise times for firing the hammers.
Another feature of the band printer includes the providing of hammers wherein a separate hammer is provided for each print position with a hammer driver for each hammer. Other band printers have utilized time shared hammer techniques wherein the hammers are of multiwidth and span more than one print column position or single width hammers which are movable to more than one print position and are arranged in a bank of hammers with such bank being movable or displaced along a line of printing.
Representative prior art in the area of band printers include U.S. Pat. No. 3,919,933, issued Nov. 18, 1975, to J. T. Potter, which discloses a high speed printer incorporating a type font having an increased number of character spaces for unit length of print line to increase the printing speed. The printing speed is increased by reducing the dimension of character spaces to the size of textbook print with an individual hammer corresponding to each printing character space.
U.S. Pat. No. 4,064,800, issued Dec. 27, 1977 to S. W. Paccione et al, discloses a printer which prints in either direction and which utilizes a barrel cam to shuttle print hammers back and forth across the paper, and several actuators are time-shared among the various print columns of the paper so that there is time sharing of the hammers.